Piston rod sealing device



1965 E. o. AMELUNG ETAL 3,

PISTON ROD SEALING DEVICE Filed March 15, 1962 jzz/ezj ors.

Jaz s Dada/21y, 6, \l65t9f 657 M W complicated. V r l I Sleeve seals stifiened by means of metallic supporting example, in-hydraulic shock absorbers.

V messes Patented Jan. 19, 1965 3,166,360 PISTON ROl) SEALING DEVICE rnst Dieter Amelung, Opladen, Hans Deuring, Bur- 7 9 Claims. (a. see-3.5

The invention disclosed herein relates to the sealing of piston rods and isparticularly concerned with sealing means for piston rods for hydraulic oscillation dampers or shock absorbers of motor vehicles, comprising a sealing lip which is pressed in sealing position by the -pres-.

sure of the medium against which the seal is efiectivei The reciprocating rod is in prior hydraulic, shock absorbers sealed by means of an elastic rubber seal, such seal having usually two lips, one of such lips, which is loaded by means of a spring, being intended for preventing the outflow of the damping fluid, while the other lip protects the interior of the device against theingress of dust and the like/ 7 While such seals operate well in ordinary practical use, they are not adapted for modern high pressureshock absorbers. High pressure shock absorbersare usually provided withan air cushion which may be separated Seals from the hydraulic fluid by an elastic bellows. which are suitable for such absorbers are predominantly provided with a sealing lip which is not spring loaded thereagainst by-an elastic washer which expands radially,

under the action of th'e' hydraulic pressure. While such seals arerelatively eiiective in thepresence of higher pressures, they have not gained general acceptance since they suffer from the drawback sheet, and having two sealing lips andintermediate stop butters, are likewise known. However, the*1ips"of such. sleeve, seals are relatively long and thin, and the end faces of the lips extend perpendicularly to thesurface of the'rod, thus permitting the hydraulic pressure to become effective over the entire surface of'the lip, necessa'rily resulting in great wear. Such se als can hardly be used for sealing against higher pressures.

Sleeve seals provided with two sealing lips without metallic stifiening are "also known, such seals requiring special holding or supporting meansso as top re've'nt shifting of the adhering part. The end face of the lips is-in suchstructures inclined with respect to the free surface of the rod, so as to provide more material in -the' region of thellips, Withqthd intention oirincreasing the pressure of lip at the rod circumference. The legs of the lips are subjected to the full'pres'sure ofthe hydraulic medium, making suchseals unsuitable for use in scheid, near qlologne, and Jose? Pafirath, Bergischthat they are structurally since the pressure of the fluid mediumsuflices to press 7 the sealing lip-against the rod which is to be sealed.

Other known seals; are composed of two different, parts,

the part thereof which lies against the rod being'pres'sedfi taken together.

2 ing position, in known manner, an angle with the free rod circumference which is smaller than 90, the area of the lip which is in engagement with the rod being greaterthan the projection area of the end face of the lip on the I rod, and the area of the lip which is radially affected by the hydraulic medium being smaller than the engaging area and the projection area of the end face of the lip The advantage of this particular configuration of the lip is that the hydraulic relief of the end face of the lip decreases with progressive Wear and that a loading is in the same measure produced, whereby the pressure exerted by the lip can be maintained constant over a Wide range. It is to be observed, however, that the lip isto be made relatively short and radially strong so as to avoid drawing thereof into the gap between the seal and the rod.

Such lips are exclusively affected by the pressure of the hydraulic medium and the auxiliary spring can therefore be omitted. However, the invention may also be advantageously used in connection with spring loaded lips. The outer diameter of the seal may be wholly or partially larger than the inner diameter of the cylinder tube, so that the seal engages the cylinder wall with pressure, thus preventing outflow of the damping fluid. This efiect may be in most simple manner supported by forming the outer part of the seal likewise in the manner of a lip.

' In order to avoid damaging the sealing lips by impact of-the piston, it is moreover proposed to provide between 30, the sealing lips a stop.made of the same material as the lips and extending axially beyond the radial plane thereof. Such stop can elastically absorb impacts of the piston l without detrimentally affecting the sealing lips. The

pressure of the hydraulic medium is in such structure positively applied 'along'annular grooves extending be- V tween the stop buffer and the respective sealing lips; such grooves permitting radial yielding or expansionmotion of the buffer, which contributes towards-holding the sealing'lips in their sealingposition.

It has also been found of advantage to line the inner face" ofthe metallic supporting sheet with an elastic material inord er tolavoidinetalli c engagement with the piston the presence of higher pressures suchasthey obtain, for

sealing. lip extending'circumferentially respectively inside and outside thereof, suchlips being affected by the'pres sure of the hydraulic'medium. In order to improve such seals, it is in accordance withthe invention proposed "to provide a'structure wherein the end iaceof the sealing lip; which is directed toward the rod embraces in operatrod, as such metallic engagement might"produce grooves in the piston rod'wliich could easily result in damage to the material of the sealing lip.

The piston rod of theshock absorber is in most cases secured against radial tipping by .a rod guide. Whenever. the seal is to be provided for particularly high pres- ;fsures, the inner sealing lip may besealedby a collarlike part of the rod guide, in such a manner, that the pressure on the lip is absorbed by s'uch part, thereby pre: venting squeezing of the-lip into the gap between the guide and the. rod. 1

. In the event that the seal is to be made lrelatively stiff in radial direction, the metallic support may be, made in steppedmanner, thereby forming in the area of'thestop' buffer a hump-like portion which carrbelmatched'to the shape offthe respective buffer.

' Thestep like configuration of the metallic support provides the] further advantage that the sealcan be placed in most simple manner upon asection of therod guide Without requiring any tunther fastening means. over, it is in this way possible to shorten the axial dimensions of the seal as wellas oi the rod guide.

Theannu'lar grooves between the ,two lips and the stop butfermayb'e made of substantially the same depthj so" 3 3 that they termin'ateusubstantially along a commonraa dialplane. It is however likewise possible to make the. annular groove between the outer lip and the stopbulfer deeper than the groove between the stop butter and the- .inne'r lip, so thatthe hydraulic pressure. exertsat such More ' .1 Changes may 4 i I theappended claims which define what is believed-tbe I new andidesired to-have,protectedby'Letters Patent. i

It is moreover entirely possible to arrange the seal.

floating between the piston rod and the cylindrical tnbe of the dampen'without necessarily 'requiring mechanical connection with these parts or with the rod guide, thus facilitating the automatic settingofthe seal.

Further'details will appear from the description of embodiments which will be rendered below with reference to the accompanying drawing.

FIG. 1 shows a seal according to the invention comprising a metallic support bent at'right angle; 7

FIG. 2 illustrates a seal having a metallic support which extends in the manner of hump;

FIG. 3 represents a seal in which the sealing lip is supported by the rod guide; and

FIG. 4 shows a sealing lip in cross-sectional view.

Referring now to the drawings, between the piston rod 1 and the cylinder tube 2 is provided the sealing memher 3, having sealing lips 4 and 5 which prevent the outflow of hydraulic iiuid from the space Both sealing lips 4 and 5 are pressed against respectively associated surfaces, exclusively by the pressure of the hydraulic fluid, such pressure supporting the inherent tension'of'the lips.

, The sealing lip has two surfaces, extending angularly i with respect to the piston rod 1,'the end face of the sealing lip. extending, in position assembled with the piston rod, at an angle whichis smaller than 99. The projection of the end face extending to the piston road at an. angle from. theedge d' of the sealing lip to the transition edge 4", is in assembled position of the seal,"srnallerthan the, area of engagement of the sealing lipon the piston rod,

' so as to avoid endangering the equalization or compensation between the loading and relief of the sealing lip in v the presence, of a pressure acting too strongly in lifting I sense; The sealing member 3 is connectedfwith a metallic We claim:

1. A sealing device for piston rods of hydraulic shock absorbers for motor. vehicles, comprising a cylindrical tube, a piston rod, an annular sealing member positioned between the wallsof the tubeand piston rod, said annular sealingmemberbeing made of elastic material which is stiifened by a metallic disk-like support joined therewith, an inner sealing lip formed by said sealing member for sealing engagement with said piston rod, said sealing lip being adapted to be acted upon by the pressure of a hydraulicrnedium, the end face of said sealing lipembracing' with the free surface of said piston rod 'anangle which is less than 96?, the area of engagement of the lip with said piston rodbeing greater than the projectior i area of the end face of the lip on'said piston rod, and the radially outwardly extending area from the area of engagement and the projection area of the sealing lip which is adapted to be acted upon by the hydraulicmedium being greater than i the projection area and smaller. than the engaging area support 7 which is vulcanized thereto, the angularly shaped metallic support being firmly disposed uponthe, stepped rod guide 8. The inside edge as Wellas the peripheral oute'nedge' of the'metalli'c support 7 arecoated and the projection area taken together.

2. A sealing device according to' claim 1, wherein the inneredge of said metallic support is' covered by part of the material of said lip. i

. .3.'A sealing deviceaccording to claim.2, 'in combination with a. guide member for said piston rod, said guide mernber carryng said sealing member, and a collar-like extension projecting from said guide member :for supporting said sealing lip.

4. A sealing device according toclaimZ, wherein said sealing device is disposed within a cylindrical tube, in

combinationwith a guide member for said piston rod, said guide member carrying said sealing ;member,; and means i for securing said guide member in engagement with said tube. i

5.. A sealingdevice according. LO claim- 1, the outer diameter of saidv sealing'member being atleastrin part greater than the innerdiarneter 'ofsaid tube.

6. A; sealing devicefaccording to claim- 5, comprising an'o'uter sealing lip formed by saidsealing member for withelastic materialas indicated respectively are and 10; I:

' The rod guide 8 is secured 'againstZ'aXial displacementby i means of a split ring. 11. j 1 I The seal shown in FIG. Zgdiifers from the one repreisented in FIGJ'LI merely in the provision of a metallic 7 support 7 which. is formed hump-like. in the area of -the' stop buffer 12) The sealingrnember 3 is thereby radially stiffened and prevents the material of the buffertlZ from i influencing the sealing lip 4. i

InpFIG. 3, thegrooves, is, is between the lips a arid 5 are of different depth, whereby the sealing lip 4 can be" pressed stronger against the pistonrod by the pressure of show pressure of. the hydraulic medium. Moreover, the

I the hydraulic medium. Arrows .on'the respective-figures? sealing engagement with the inner wall of said tube, and an enlargement formed on said sealing member between; said sealing lips, said enlargement egttending axially beyond the plane of said sealing lips and forminga stop for impact engagement with the 7 piston cooperatively assojciated with said piston rod.

7. A sealing deviceaccording to cilaim '5, comprising an outer sealing-lip formed by said sealing member for sealing engagement with the-inner Wall ofsaid-tube, an

annular'gr'oove formed in saidisealing member adjacent said'outer sealinglip, the .material of said sealing member extending axially beyond the plane ofsaid sealing lips andforming astop for'protecting said sealing, lips against impact by the piston cooperatively associated with" said piston rod. 1.

'8. A sealing device accordingto clairn'7, wherein one 7 of said annular grooves is -deeperjthan the other.

' 'InFlG. 4, the lip '4 likewiseembrace's the piston rod 1, v

1 'l'yin'gagainst the rodll with the sectionA: .t"lh '-:"iareaof the-engaging section -A is always greater than the: projec-j tion area P of the end face plane 25 of the lip, thereby resulting in engagementwith uniform pressure over a long periodof time. .Thisisfurther supported by placin'gfthe rece s 23 outside' the'radial plane 24, so that the area L, 1

designated as the radially outwardly extending area, which member;

is 'affected'by the hydraulic medium, isalways srnaller than the engaging area A and the projection area .1? taken to}.

gether. 7

e made within the scope and spirit '01:

7o SUS K O, Primary xammer,

9. Ascaling deviceaccordingtoclaim 7, wherein said metallic support is angularly shaped forming a hump-like portion with the area of said stop formed by said sealing" -R referencesCitetilbythe I V UNITED s'rArEsPATENTs l V 2,078,364 7 14/37 Becker r 2,467,210 4/49- Helfrecht 27 7-235 2,907,596 10/59 Mah a .277'205 2,992,864 7/61 De Carbon 3 O8-3.5 3,003,799 10/61 Marchionda 277205:X 3,104,881 9/63 English"; 

1. A SEALING DEVICE FOR PISTON RODS OF HYDRAULIC SHOCK ABSORBERS FOR MOTOR VEHICLES, COMPRISING A CYLINDRICAL TUBE, A PISTON ROD, AN ANNULAR SEALING MEMBER POSITIONED BETWEEN THE WALLS OF THE TUBE AND PISTON ROD, SAID ANNULAR SEALING MEMBER BEING MADE OF ELASTIC MATERIAL WHICH IS STIFFENED BY A METALLIC DISK -LIKE SUPPORT JOINED THEREWITH, AN INNER SEALING LIP FORMED BY SAID SEALINGMEMBER FOR SEALING ENGAGEMENT WITH SAID PISTON ROD, SAID SEALIN GLIP BEING ADAPTED TO BE ACTED UPON BY THE PRESSURE OF A HYDRAULIC MEDIUM, THE END FACE OF SAID SEALING LIP EMBRACING WITH THE FREE SURFACE OF SAID PISTON ROD AN ANGLE WHICH IS LESS THAN 90*, THE AREA OF ENGAGEMENT OF THE LIP WITH SAID PISTON ROD BEING GREATER THAN THE PROJECTION AREA OF THE END FACE OF THE LIP ON SAID PISTON ROD, AND THE RADIALLY OUTWARDLY EXTENDING AREA FROM THE AREA OF ENGAGEMENT AND THE PROJECTION AREA OF THE SEALING LIP WHICH IS ADAPTED TO BE ACTED UPON BY THE HYDRAULIC MEDIUM BEING GREATER THAN THE PROJECTION AREA AND SMALLER THAN THE ENGAGING AREA AND THE PROJECTION AREA TAKEN TOGETHER. 